The quaternary material system In[subscript x]Ga[subscript 1-x]As[subscript y]P[subscript 1-y] is an important material system for optoelectronic devices, specifically covering optimum fiber optic wavelengths. Among the limitations of using this material system concerning photodetector performance is generation of carriers due to material defects and impurities. This dissertation reports on the growth optimization of InGaAs using molecular-beam epitaxy for low-dark-current avalanche photodiodes through the study of the effects of the growth conditions on dark current. An optimum growth temperature of 545°C and arsenic beam equivalent pressure of 2x10⁻⁵ Torr was found for producing the lowest dark current density. Avalanche photodiodes were implemented with a dark current density 80 mA/cm² at 90% of the breakdown voltage.